Side branch stent graft

ABSTRACT

A joining arrangement between a main tube ( 3 ) and a side arm ( 5 ) in a side arm stent graft ( 1 ). The side arm ( 5 ) is stitched into an aperture ( 11 ) in the main tube and is in fluid communication with it. The aperture is triangular, elliptical or rectangular and the side arm is cut off at an angle to leave an end portion having a circumferential length equal to the circumference of the aperture. The side arm can also include a connection socket ( 76 ) comprising a first resilient ring ( 79 ) around the arm at its end, a second resilient ring ( 80 ) spaced apart along the arm from the first ring and a zig zag resilient stent ( 82 ) between the first and second rings. The zig-zag resilient stent can be a compression stent. Both the main tube and the side arm are formed from seamless tubular biocompatible graft material.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims priority of provisional application Ser. No.60/611,774, filed Sep. 21, 2004.

TECHNICAL FIELD

This invention relates to a stent graft used to restore the patency of abody lumen and in particular relates to a side branch or side arm stentgraft.

BACKGROUND OF THE INVENTION

Where damage has occurred to an internal vessel of the human or animalbody such as a blood vessel either by disease or by trauma it ispossible to introduce to the blood vessel a stent graft by endoluminaltechniques which will restore patency of the blood vessel across thedamaged region. Often such damaged regions include side branch vessels.To ensure the blood flow can go into the side branch vessel side branchstent grafts are used.

There can be a problem with such side branch stent grafts that in theregion of the bifurcation or exit of a side branch from a main tube,disruption to blood flow can occur. This may result in thrombosisoccurring which could at least partially block the stent graft. Also,without suitable geometry, blood flowing through such regions may notadequately flow into the side arm or side branch.

It is the object of this invention to provide a branched or side armstent graft which does not compromise blood flow in the main lumen ofthe stent graft and allows blood flow into the side arm.

Throughout this specification the term distal with respect to a portionof the vasculature, a deployment device or a stent graft is the end ofthe vasculature, deployment device or stent graft further away in thedirection of blood flow away from the heart and the term proximal meansthe portion of the vasculature, deployment device or end of the stentgraft nearer to the heart. When applied to other vessels similar termssuch as caudal and cranial should be understood.

SUMMARY OF THE INVENTION

In one form therefore the invention is said to reside in a side armstent graft comprising a main tube of a biocompatible material and aside arm tube of a biocompatible material extending from the main tubeat an acute angle thereto and being stitched thereto and in fluidcommunication therewith, wherein the stent graft further comprises atriangular aperture in the main tube around the periphery of which theside arm tube is stitched, the triangular aperture having a base and apair of sides, and an end of the side arm tube having a bevel to leavean end portion having a circumferential length equal to the length ofthe base of the triangular aperture and a length of the bevel equal tothe length of the side of the triangular aperture, whereby the side armtube is stitched to the main tube around the periphery of the triangularaperture with the end portion abutting the base of the triangularaperture and the bevel abutting the sides of the triangular aperture.

In an alternative form the invention is said to reside in a side armstent graft comprising a main tube of a biocompatible material and aside arm tube of a biocompatible material extending from the main tubeat an acute angle thereto and being stitched thereto and in fluidcommunication therewith, wherein the stent graft further comprises anelongated aperture in the main tube around the periphery of which theside arm tube is stitched, the elongate aperture having acircumferential length, and an end of the side arm tube having a bevelto leave an end portion having a circumferential length equal to thecircumferential length of the elongate aperture, whereby the side armtube is stitched to the main tube around the periphery of the elongateaperture.

In an alternative form the invention comprises a side arm stent graftcomprising a main tube of a biocompatible material and a side arm tubeof a biocompatible material extending from the main tube and beingstitched thereto and in fluid communication therewith, wherein the stentgraft further comprises an elongate aperture in the main tube and anangled inner end on the side arm tube, the periphery of the inner end ofthe side arm tube being stitched to the periphery of the aperture,whereby the circumference of the joined region of the main tube and sidearm tube increases along the length of the stitching at a first end ofthe joined region, to the sum of the circumferences of the main tube andthe side arm tube at the other end of the joined region.

In one embodiment the elongate aperture is substantially rectangular.

In an alternative embodiment the elongate aperture is substantiallyelliptical.

In a further embodiment the elongate aperture is substantiallytriangular.

The acute angle may be in the range of from 15 to 60 degrees andpreferably 15 to 45 degrees.

In a further form the invention is said to reside in a side arm stentgraft comprising a main tube of a biocompatible material, a fenestrationin the main tube defined by a peripheral edge to the fenestration and aside arm tube of a biocompatible material being joined around theperipheral edge at a join region by stitching and extending from themain tube at an acute angle thereto and in fluid communication with themain tube, whereby the circumference of the join region of the main tubeand side arm tube increases along the length of the stitching at a firstend of the joined region from the circumference of the main tube to thesum of the circumferences of the main tube and the side arm tube at theother end of the join region.

Preferably the fenestration can be selected from an elongate aperture, asubstantially rectangular aperture or a substantially ellipticalaperture. Alternatively the fenestration may be substantiallytriangular.

It will be seen that by this invention there is provided a main flowlumen whose circumference increases from that of the main flow tube orstent graft to that of the sum of the main flow tube plus the side armtube before the actual side arm tube flow branches off. By thisarrangement the flow of blood through the replacement vessel is enabledto flow both through the main branch and into the side arm withoutsignificant interruption.

Biocompatible graft material such as dacron is available in tubular formand hence it is relatively straight forward to cut the aperture in alength of the tubular material of a first diameter and to cut a bevel inthe end of a piece of tube of another diameter and to join thenaccording to the present invention.

The side arm stent graft preferably further comprises a plurality ofself expanding stents along the main tube, one of the self expandingstents extending around both the main body and the side arm. Preferablythe self expanding stent extending around both the main body and theside arm comprises a bend adjacent to the proximal end of the stitchingand the struts extending down either side of the side arm.

In a further form the invention is said to reside in a method ofassembling a side arm stent graft comprising the steps of:

forming a triangular aperture in a main tube, the triangular aperturebeing defined by a base and a pair of sides;

forming a bevel cut out on a side arm tube to define a remaining endpiece and beveled edges;

stitching the beveled edges to the sides of the triangular aperture; and

stitching the remaining end piece of the side arm tube to the base ofthe triangular aperture.

Preferably the method further includes the step of turning inside outthe side arm and inserting it into the main tube such that the remainingstraight end at the bevelled end piece of the side arm is aligned withthe base of the triangular aperture and the bevelled edges are alignedwith the sides of the triangular aperture before the stitching steps.

Preferably both the main tube and the side arm tube are formed from aseamless tube of a biocompatible graft material.

BRIEF DESCRIPTION OF THE DRAWING

This then generally describes the invention but to assist withunderstanding reference will now be made to the accompanying drawingswhich show various embodiments of the invention.

In the drawings:

FIG. 1 shows schematically a main tube and a side branch for a stentgraft;

FIG. 2 shows a side view of the embodiment shown in FIG. 1;

FIG. 3 shows a view of the embodiment shown in FIGS. 1 and 2 with theside arm stitched into the main tube;

FIGS. 4A to F show the circumferences of the main tube and side arm atvarious positions along the joining region of the main tube and side armtube.

FIGS. 5, 6 and 7 show an alternative form of connection of a side arm toa main tube according to the present invention;

FIG. 8 shows a front elevation of a side branch stent graft madeaccording to the connection arrangement shown in FIGS. 5, 6 and 7;

FIG. 9 shows a side elevation of a side branch stent graft madeaccording to the connection arrangement shown in FIGS. 5, 6 and 7;

FIGS. 10, 11 and 12 show a still further arrangement of joining of aside arm tube to a main tube;

FIG. 13 shows a side branch stent graft or prosthesis of the typeadapted for deployment into the iliac arteries and including oneembodiment of the present invention; and

FIG. 14 shows an alternative form of stent graft having side branchesconnected to a main tube according to one embodiment of the presentinvention.

DETAILED DESCRIPTION

Now looking at the drawings and more particularly the first embodimentshown in FIGS. 1 to 4 it will be seen that the stent graft 1, accordingto one embodiment of the present invention, comprises a biocompatiblegraft material main tube 3 and a side arm 5 also comprises abiocompatible graft material.

For the purpose of assisting in the explanation of the present inventionthe stent graft main tube 3 has a proximal end 7 and a distal end 9 andblood flow would normally be from the proximal end 7 to the distal end9.

To join the branch tube 5 to the main tube 3, according to oneembodiment of the invention, a triangular aperture or fenestrationgenerally shown as 11 is cut into the main tube 3. The triangularaperture or fenestration 11 is in the shape of an isosceles trianglewith the base 13 at the proximal end and the substantially equal lengthsides 15 more distal. The side arm 5 has a bevel cut in it at one of itsends such that the remainder 18 of the circumference of the side armafter the bevel 17 is cut into the side arm has a semi-circumference 19which is substantially equal to the length of the base 13 of thetriangular aperture or fenestration 11. The length of the bevel 17 issubstantially equal to the length of the sides 15 of the triangularaperture or fenestration 11.

FIG. 2 shows a side view with the side arm 5 offered up to the aperture11 in the main tube 3.

FIG. 3 shows the side arm 5 stitched into the main tube 3 and it will benoted that the stitching 16 extends along the base 13 of the triangularaperture or fenestration 11 on the main tube and then along the sides 15of the isosceles triangle.

FIG. 3 shows the positions of cross-sections a-a′, b-b′, c-c′, d-d′,e-e′ and f-f′ and these cross sections are shown in FIGS. 4A to F.

FIG. 4A shows the circumference of the main tube 3. FIG. 4B shows themain tube 3 plus the region 19 of the side arm 5 stitched on.

Through FIGS. 4C and D the diameter of the added portion increases untilin FIG. 4D the circumference of the tube is substantially equal to thetotal of the circumferences of both the main tube 3 and side tube 5. At4E the side tube commences to branch off and at 4F the side tube 5 hascompletely branched off from the main tube 3. By this arrangement thecross sectional area of the lumen of the stent graft increases toessentially that of the sum of the main tube and side arm before theside arm branches off and by this arrangement there is not significantobstruction to blood flow and blood is able to flow into the side armeasily.

In practice a self-expanding stent 21 is placed on the outside of thestent graft at the branch or join region to assist with maintaining theside arm and main tube in a more circular cross section and as open aspossible as shown in FIGS. 3 and 4D.

FIG. 3 also shows other self-expanding stents on the main body of thestent graft. These include a proximal stent 23 and more distal stents 24and 25. The actual number of stents would depend upon the length of themain tube proximally and distally of the region of the join of the sidearm. In the case of a stent graft to be deployed into the common iliacartery with the side arm adapted to extend towards the internal iliacartery normally there would only be a short length of main tube and asingle stent proximal of the join to the side arm.

In this embodiment the side arm extends from the main tube 3 at an angledesignated by the numeral 26. This angle may be in the region of from 15to 45 degrees.

In one particular embodiment the main tube 3 may have a diameter of 12mm and hence a circumference of 38 mm. The side tube may have a diameterof 8 mm and hence a circumference of 26 mm. The base of the triangularaperture or fenestration 11 may have a length of 13 mm and the sides ofthe triangular aperture or fenestration 11 may have a length of 20 mm.Hence the side arm 5 has a bevel cut into it leaving a semicircumference 19 of 13 mm and a length of the bevel 17 of 20 mm. Thestent graft may have an overall length of 103 mm. In the case of a stentgraft to be deployed into the common iliac artery with the side armadapted to extend towards the internal iliac artery normally there maybe a length of main tube of 16 mm proximal of the join to the side armand up to 68 mm distal of the join to the side arm. The side arm mayhave a diameter of 8 mm and a length distally of the join region of upto 25 mm. It will be realised that for stent grafts to be deployed intothe ascending or descending aorta with side arms to extend into theirrespective branch vessels, other lengths and diameters will beapplicable.

One method by which the side arm stent graft according to the presentinvention may be assembled by stitching is as follows:

-   -   The triangular aperture is cut out of the main tube and the        bevel cut out of the side arm.    -   The side arm is turned inside out and inserted into the main        tube such that the remaining straight end at the bevelled end of        the side arm is aligned with the base of the triangular aperture        and the bevelled edges are aligned with the sides of the        triangular aperture.    -   The two tubes are temporarily tacked together.    -   The bevelled edges are stitched to the sides of the triangular        aperture.    -   The bevelled end of the side arm is stitched to the base of the        triangular aperture.    -   The side arm is then pulled out through the aperture.    -   The necessary stents are then stitched to the main tube and the        side arm.

Both the side arm 5 and the main tube 3 are formed from a seamless tubeof a biocompatible graft material. This means that when the stent graftis compressed into an endovascular delivery device seams along thelength of the tube do not compromise the size of the stent graft.

FIGS. 5, 6, 7, 8 and 9 show an alternative embodiment of branch stentgraft according to the present invention.

In this embodiment the stent graft 30 has an elongate ellipticalfenestration or aperture 31 which is cut in the main body 32 and a sidearm 34 has a angled and curved cut end 36 such that the circumference ofthe elliptical fenestration 31 is substantially the same length as thecircumference of the angled and curved end 36.

FIG. 7 shows the side arm 34 stitched into the main body 32 withstitching 38.

FIG. 8 shows a front elevation and FIG. 9 shows a side elevation of aside branch stent graft made according to the connection arrangementshown in FIGS. 5, 6 and 7. After the side arm 34 has been sewn into themain tubular body 32 by stitching 38 around the periphery of theaperture 31 (FIG. 5) and the circumference of the angled and curved end36 (FIG. 6), self expanding zig-zag Z stents 39 are sewn onto theoutside of the tubular body 32 except for the distal-most stent 40 whichis mounted internally. It will be noted that the stent 41, in theposition in which the side arm extends from the main tubular body,extends around both the main tubular body 32 and the side arm 34.

In particular it can be noted that the stent 41 has a bend 43 betweenstruts 44 and 45 adjacent to the proximal end of the stitching 38 andthat the struts 44 and 45 extend on either side of the side arm 34.

By this arrangement the circumference of the main body and side armincreases from being the circumference of the main body at the proximalend of the join region until at the distal end of the join region, thetotal circumference is the circumference of the main body plus thecircumference of the side arm and it is after this that the side armactually exits.

FIGS. 10, 11 and 12 show a further embodiment of the present invention.In this embodiment the stent graft 40 has an elongate substantiallyrectangular slot 51 formed in the main tube 52 and a side arm 54 has abevelled or angled end 56 which is stitched into the main body as shownin FIG. 12 using stitching 58. The bevelled end 56 has a circumferencewhich is substantially the same length as the length of the periphery ofthe aperture 51.

FIG. 13 shows a side branch stent graft or prosthesis of the typeadapted for deployment into the iliac arteries, for instance, such thata bridging stent can extend from the side arm into the internal iliac orhypogastric artery.

The stent graft 70 has a main tubular body 72 and a side arm 74. Boththe main tubular body and the side arm are formed from a seamless tubeof a biocompatible graft material such as Dacron. A triangular apertureis formed in the main tube and a bevel cut into the inner end of theside arm and the side arm stitched into the triangular aperture withstitching 78 according to the method of the present invention. The sidearm has a connection socket arrangement 76 at its distal end 77. Theconnection socket arrangement 76 comprises a first resilient ring 79stitched to its terminal or distal end 77 and a second resilient ring 80spaced apart from the first ring 79. Each ring 79 and 80 is formed fromat least two turns and preferably three turns of nitinol wire and theends of the nitinol wire terminate in loops 81. The use of the loops 81prevents sharp ends from the nitinol wire from digging into thevasculature into which the stent graft is deployed. Between the firstring 79 and the second ring 80 is a stent 82 formed from a resilientmaterial. The resilient stent 82 is formed from nitinol wire, forinstance, and is made to be of a size which is at rest slightly smallerthan the diameter of the side arm 74 and hence when sewn on to theoutside of the side arm 74 it provides a diameter reducing effect on theside arm 74.

When a bridging stent such as a balloon expandable stent is placed intothe socket 76 and expanded, the rings 79 and 80 provide firm locking forthe balloon expanded stent and the resilient stent 82, which is expandedby the balloon expanded stent while it is being balloon expanded,provides a compressive effect to keep tension on the balloon expandedstent. By this means a firm connection can be obtained between the sidearm and a bridging stent. A similar gripping effect can be obtained withthe use of a bridging stent in the form of a self-expanding stent, acomposite stent or other form of leg extension.

FIG. 14 shows an alternative form of stent graft having a number of sidebranches according to the present invention. This form of stent graft isadapted for deployment into the mid-aorta region where major vesselsbranch off the aorta. In this embodiment the stent graft 90 has a pairof tapered regions 92 and 94. At the taper 92 a pair of side branches 96and 98 branch off and at the taper 94 a further pair of side branches100 and 102 branch off the main tube. The side branch 96 is intended forconnection to the superior mesenteric artery, the side branch 98 isintended for connection to the coeliac artery, the side branch 100 isintended for connection to a renal artery and the side branch 102 isintended for connection to the other renal artery. Each of the four sidebranches 96, 98, 100 and 102 are joined to the main tube by anarrangement similar to that shown in FIGS. 1 to 3. In each case,however, as the main tube is tapered the side branches extend atsubstantially the same angle as the main tube.

In the case of each side arm a triangular aperture is formed in the maintube and a bevel cut into the inner end of the side arm and the side armstitched into the triangular aperture with stitching 104 according tothe method of the present invention. Each side arm has a connectionsocket arrangement 106 at its distal end. The connection socketarrangement 106 comprises a first ring 108 stitched to its terminal ordistal end and a second ring 110 spaced apart from the first ring 108.Each ring 108 and 110 is formed from at least two turns and preferablythree turns of nitinol wire and the ends of the nitinol wire terminatein loops. The use of the loops prevents sharp ends from the nitinol wirefrom digging into the vasculature into which the stent graft isdeployed. Between the first ring 108 and the second ring 110 is a stent112 formed from a resilient material. The resilient stent 112 is formedfrom nitinol wire, for instance, and is made to be of a size which is atrest slightly smaller than the diameter of the side arm 98 and hencewhen sewn on to the outside of the side arm 98 it provides a diameterreducing effect on the side arm 98.

The main stent graft has a series of self expanding stents 114 along itslengths and it will be particularly noted that self expanding stentsextend over the junction regions of the side arms to assist with holdingthe side arms open to blood flow.

Throughout this specification various indications have been given as tothe scope of this invention but the invention is not limited to any oneof these but may reside in two or more of these combined together. Theexamples are given for illustration only and not for limitation.

Throughout this specification and the claims that follow unless thecontext requires otherwise, the words ‘comprise’ and ‘include’ andvariations such as ‘comprising’ and ‘including’ will be understood toimply the inclusion of a stated integer or group of integers but not theexclusion of any other integer or group of integers.

1. A side arm stent graft comprising a main tube of a biocompatible material and a side arm tube of a biocompatible material extending from the main tube at an acute angle thereto and being stitched thereto and in fluid communication therewith, wherein the stent graft further comprises an elongate aperture in the main tube and having a periphery around which the side arm is stitched, the elongate aperture having a circumferential length and an end of the side arm tube including a beveled end portion having a circumferential length equal to the circumferential length of the elongate aperture, whereby the side arm tube is stitched to the main tube around the periphery of the elongate aperture.
 2. A side arm stent graft as in claim 1 wherein the elongate aperture is substantially rectangular.
 3. A side arm stent graft as in claim 1 wherein the elongate aperture is substantially elliptical.
 4. A side arm stent graft as in claim 1 wherein the elongate aperture is substantially triangular.
 5. A side arm stent graft as in claim 1 wherein the elongate aperture comprises a triangular aperture in the main tube around the periphery of which the side arm tube is stitched, the triangular aperture having a base and a pair of sides, wherein an angled inner end on the side arm tube comprises an end portion having a length equal to the length of the base of the triangular aperture and a beveled portion having a length equal to the length of the side of the triangular aperture, whereby the side arm tube is stitched to the main tube around the periphery of the triangular aperture with the end portion abutting the base of the triangular aperture and the beveled portions abutting the sides of the triangular aperture.
 6. A side arm stent graft as in claim 1 wherein the side arm tube extends from the main tube at an acute angle thereto, the acute angle being in range of from 15 to 60 degrees.
 7. A side arm stent graft as in claim 1 wherein the side arm tube extends from the main tube at an acute angle thereto, the acute angle being in the range of from 15 to 45 degrees.
 8. A side arm stent graft as in claim 1 further comprising a plurality of self expanding stents along the main tube, one of the self expanding stents extending around both the main tube and the side arm tube.
 9. A side arm stent graft as in claim 8 wherein the self expanding stent extending around both the main tube and the side arm tube comprises a bend adjacent to a proximal end of the stitching and struts extending down either side of the side arm tube.
 10. A side arm stent graft comprising a main tube of a biocompatible material and a side arm tube of biocompatible material extending from the main tube at an angle thereto and stitched thereto and being in fluid communication therewith, wherein the side arm stent graft further comprises a triangular aperture in the main tube around the periphery of which the side arm tube is stitched, the triangular aperture having a base and a pair of sides, and an end of the side arm tube having a bevel to leave an end portion having a circumferential length equal to the length of the base of the triangular aperture and a length of the bevel equal to the length of the side of the triangular aperture, whereby the side arm tube is stitched to the main tube around the periphery of the triangular aperture with the end portion abutting the base of the triangular aperture and the bevel abutting the sides of the triangular aperture.
 11. A side arm stent graft comprising a main tube of a biocompatible material and a side arm tube of a biocompatible material extending from the main tube and being stitched thereto and in fluid communication therewith, wherein the side arm stent graft further comprises an elongate aperture in the main tube and an angled inner end on the side arm tube, the periphery of the inner end on the side arm tube being stitched to the periphery of the aperture whereby the circumference of the joined region of the main tube and side arm tube increases along the length of the stitching at a first end of the joined region to the sum of the circumferences of the main tube and the side arm at the other end of the joined region. 